The present invention resides generally in the field of medical devices and methods, and particularly to methods that can be used in the implantation of medical devices in the spine to treat a variety of conditions.
As further background, much of the population will experience back pain at some point. There are many causes for back pain, and many treatments for alleviating the pain. Seven cervical, twelve thoracic, and five lumbar vertebrae are included in the normal human spine. Intervertebral discs reside between adjacent vertebrae except for in the first articulation between the first two cervical vertebrae. A disc also lies between the last lumbar vertebrae and the sacrum. Diseases or disorders in any of these or other areas of the spine can cause debilitating pain as well as limited mobility in a patient.
In one field of therapy, medical devices are implanted in the spine at one or more locations to treat the spinal condition. A variety of medical devices are utilized, serving a variety of purposes. Illustratively, fusion cages and other interbody fusion devices are positioned between vertebrae to facilitate their fusion. Such devices are commonly employed in conjunction with rods, screws, hooks, or plates that are also connected to elements of the spine. Systems are also connected to the spine in the absence of fusion devices, so as to support or realign elements such as vertebrae.
Disc nucleus implants are also known, for receipt within the interior space of a damaged or otherwise ineffectual intervertebral disc. Many such devices that have been proposed are formed of hydrogels or elastomeric polymers, for absorbing impact and other forces occurring between the vertebrae.
While there is a wide variety of spinal implant devices, most have in common the feature of transferring or imparting forces to bony tissue occurring within vertebrae of the spine. These forces may at times be deleterious to those bony tissues, particularly for example in the case of patients having diseased or damaged bony tissue in critical areas of the spine.
In light of this background, there exist needs for methods for implanting medical devices in the spine in which measures are undertaken to minimize the risk that loads imparted to bony tissue by the medical devices will cause fracture or other injury to the bony tissue. The present invention is addressed to these needs.